vine: lib tasks coffea casa minor fixes (#3779)

* vine: use cores as fallback for slots in dask executor

* vine: set environment variables for libraries in dask executor

* fix env var call

taskvine/src/bindings/python3/ndcctools/taskvine/dask_executor.py

@@ -177,12 +177,21 @@ def _dask_execute(self, dsk, keys):
             if self.lib_resources:
                 if 'cores' in self.lib_resources:
                     libtask.set_cores(self.lib_resources['cores'])
+                    libtask.set_function_slots(self.lib_resources['cores'])  # use cores as  fallback for slots
                 if 'memory' in self.lib_resources:
                     libtask.set_memory(self.lib_resources['memory'])
                 if 'disk' in self.lib_resources:
                     libtask.set_disk(self.lib_resources['disk'])
                 if 'slots' in self.lib_resources:
                     libtask.set_function_slots(self.lib_resources['slots'])
+                if self.env_vars:
+                    for k, v in self.env_vars.items():
+                        if callable(v):
+                            s = v(self, libtask)
+                        else:
+                            s = v
+                        libtask.set_env_var(k, s)
+
             self.install_library(libtask)
 
         enqueued_calls = []